1. Field of the Invention
The present invention relates generally to gate valves and, more particularly, to a large I.D. gate valve with a cutter operable for repeatable cutting pipe and/or wireline so as to be especially suitable for replacing an entire BOP stack in a lower riser package.
2. Description of the Background
Blowout Preventor (B.O.P.) stacks are frequently utilized in oilfield wellbore Christmas trees such as, for instance, lower riser packages in offshore wells. B.O.P. stacks may include a first set of rams for sealing off the wellbore and a second set of rams for cutting pipe such as tubing and/or cutting wireline. However, B.O.P. stacks tend to be quite bulky and heavy, which are undesirable features especially in lower riser packages for undersea operation where space is often at a premium. B.O.P. stacks tend to be expensive for initial installation. Moreover, if maintenance is required, then the maintenance costs for replacing such B.O.P. stacks can be many times the original installation costs. B.O.P. stacks may frequently require maintenance after cutting pipe is required. For instance, the cut pipe may become stuck within the B.O.P. stack blocking other operations.
While gate valves with various types of cutters have been developed including gate valves with one or more cutting edges for cutting wireline, such gate valves have not been utilized to replace B.O.P. stacks. Moreover, it would be desirable to provide a gate valve for casing such as in the 7xe2x85x9c inch range operable for cutting production tubing such as, for instance, 2xe2x85x9e inch production tubing with 0.204 wall thickness.
Consequently, those skilled in the art will appreciate the present invention that addresses the above problems.
An objective of the present invention is to provide an improved gate valve with capability of reliably and repeatable cutting tubulars of at least 2xc2xexe2x80x3 or more, if desired, without the need for maintenance.
Another objective of the present invention is to provide a large diameter gate valve suitable for replacing a B.O.P. stack containing rams for sealing the wellbore and rams for cutting tubing.
Accordingly, the present invention provides a method for a gate valve mountable onto a wellbore casing. The gate valve is preferably operable for controlling fluid and cutting tubing. The method may comprise one or more steps such as, for instance, mounting the gate valve on the well casing for controlling fluid flow without also utilizing a BOP on the well casing, mounting a slidable gate within the gate valve, providing the slidable gate may have a first side and a second side opposite the first side, providing first and second seats for the slidable gate such that the first side of the gate is preferably adjacent the first seat and the second side of the gate is preferably adjacent the second seat, providing a single cutting edge on the slidable gate of the gate valve such that the slidable gate defines an aperture through the slidable gate, positioning the single cutting edge such that the aperture has a minimum diameter at the cutting edge, forming the cutting edge adjacent the first side of the gate, and/or providing an inclined surface on the gate such that the inclined surface defines at least a portion of the aperture such that the aperture increases in diameter with respect to axial distance away from the cutting edge such that the aperture has a maximum diameter towards an opposite side of the gate.
Other steps may comprise mounting the gate valve in a subsea installation. In one embodiment the method may further comprise providing that the first seat is preferably formed by telescoping interconnecting two seat elements with respect to each other, providing that the second seat is preferably formed by telescoping interconnecting two seat elements with respect to each other, and/or providing that the aperture has a minimum diameter at the first side of the slidable gate.
In another embodiment, a method is provided for determining force needed on a gate to cut a tubular disposed within a gate valve. The gate valve is preferably mountable on a wellbore casing such that the tubular is preferably positional within the wellbore casing. The method may comprise one or more steps such as, for instance, providing a test body for slidably supporting a test gate, the test gate may comprise dimensions related to the gate, inserting a test pipe through the test body and the test gate, the test pipe may comprise dimension related to the tubular, applying force to the test gate until the pipe is cut by the test gate, and measuring the force on the test gate required for cutting the test pipe. The method may also comprise designing an actuator for the gate such that the actuator is capable of producing the force and/or utilizing a hydraulic press for applying the force to the test gate.
In another embodiment, a method is provided for cutting a pipe within a wellbore utilizing a gate valve such that the pipe is pushed away from a gate within the gate valve. The method may comprise one or more steps such as, for instance, providing the gate valve with a single cutting edge on one side of the gate along the aperture through the gate, providing an inclined surface on the aperture through the gate such that the aperture opens to a maximum diameter distal the single cutting edge, inserting the pipe into the wellbore through the gate valve, closing the gate within the gate valve, and cutting the pipe as the gate closes such that the inclined surface produces a force on the pipe to move the pipe away from the gate.
Therefore an apparatus is provided comprising a gate valve for a subsea riser package installation the subsea riser package installation may have no B.O.P. The apparatus comprises one or more elements such as, for instance, a sliding gate within the gate valve, a single cutting edge mounted on one side of the sliding gate, an inclined surface adjacent the cutting edge such that the single cutting edge and the inclined surface define an aperture through the sliding gate, and a hydraulic actuator for the gate valve operable to apply sufficient force to the sliding gate to cut the tubular. In one embodiment, the inclined surface is angled with respect to an axis through the aperture and flow path of the gate valve by from three degrees to twenty degrees.